I'm working on a digital gauge for the Subaru legacy vent. It is in the prototyping stage and should fit model years 05-09. The majority of the vent functionality is maintained, however the two top vent louvers are removed where the gauge is installed.

There are 2 graphs, one is dedicated to boost visuals. The other, could be vac, also lets you know what history location your looking at (see video).

This thing has boost peak history. You know, when you were too busy driving to catch the peak and hold, now you can just request the history.

Other features:
Max pressure readings in excess of 30 PSI
Vac readings down to 24 in hg.
Programmable alarm
Programmable peak and hold time